520 



Records of the Indian Museum 



[Vol. XVI, 



tional in size and the presence of ovarian eggs indicates that 

 they are capable of breeding and not, therefore, senile. The 

 instance appears to be one of female sexual dimorphism, a 

 phenomenon not, I believe, hitherto noticed among Decapod 

 Crustacea. 



It is very remarkable that the abdomen should be constricted 

 in the abnormal females. In males the copulatory appendages 

 can be exserted through the notches formed by the constriction 

 and can remain in this position with the abdomen folded against 

 the sternum : at the time of their capture many males of S. proxi- 

 ma were found with the appendages exposed. The modification 

 of the abdomen seems thus to have a definite function in the 

 male; in the female it is difficult to see how it can serve any 

 useful purpose. 



Of 87 specimens of S. proxima collected in Mormugao Bay in 

 Portuguese India 50 are males, 31 normal females (2 ovigerous) 

 and 6 abnormal females. Of 14 specimens from the neighbourhood 

 of Tuticorin in vS. India 9 are males, 4 normal females (i ovigerous) 

 and I an abnormal female. Of 16 specimens from Ennur back- 

 water, near Madras, 6 are males, 7 normal females and 3 abnormal 

 females. 



In large males the carapace is about 4-4 mm. in length and 7 

 mm. in breadth. 



9Si|-i; Vasco da Gama Ba)-, 

 Mormugao Bay, Portu- 

 guese India. 



osiii6 Donna Paula Ba}-, Mor- 

 mugao Bay. 



9S1-LT8 Bay N.W. of Nazareth 

 Point, Mormugao Bay. 

 ssiA Silavathurai lagoon, nr. 



Tuticorin, S. India. 

 es|L Ennur backwater, near 

 Madras. 



Both in Mormugao Bay and near Tuticorin the species was 

 found associated with Dotilla mydiroides , but the colonies of the 

 latter were situated close to low-water mark, whereas those of 

 S. proxima were higher up the beach, near high-water mark. In 

 Mormugao Bay the species was found on ground that was sandy 

 with a small admixture of mud. The burrows were widely separated, 

 with pellets of sand neatly arranged in the customary manner. In 

 many cases two, three or four 'runs' led to the mouth of the 

 burrow, in place of the single one usually found in Dotilla. The 

 ' runs' are long, sometimes as much as i ft. 



The salinity of the water in Mormugao Bay varies with the 

 state of the tide and doubtless also according to the season of the 

 year; at the time of my visit, towards the end of the monsoon, it 

 was everywhere brackish. The specific gravity in Vasco da Gama 

 Bay was on one occasion i'Oi65 (corrected). 



The types are from Vasco da Gama Bay and bear the number 

 9812/10, Zool. Sitrv. Ind. 



